1. Field of the Invention:
This invention relates to tubular heat exchangers and particularly to structural features thereof incorporating core removability with fluid pressure protection.
2. Description of the Prior Art:
In one type of tube and shell heat exchanger, a core assembly comprising spaced apart headers and interconnecting tubes is received in a shell body with provision being made for flow of a first fluid through the shell body over and around the core tubes and for flow of a second fluid through the tubes. Conventionally, metallurgical bonding is used to fix the core assembly in the shell body. This has the advantage of manufacturing simplicity and at the same time it seals the fluids from communication with one another.
In some instances, however, a heat exchanger user objects to metallurgical bonding on the ground that it effectively prevents heat exchanger disassembly and re-assembly, as for purposes of core inspection and servicing. In those instances there is substituted for metallurgical bonding a concept of O-ring sealing around header peripheries. An example of such alternate construction is shown in Pfouts, et al U.S. Pat. No. 4,029,145, dated June 14, 1977. As there indicated, header peripheries are slidably sealed to an interior wall of the shell body, and upon an end of the shell being opened up the core can be withdrawn for inspection.
What may be termed a floating core construction yields easy access to the core but is achieved at a cost of exposing core tubes and tube to header joints to potentially damaging fluid pressures. The fluids brought to the heat exchanger for heat transfer are circulated or supplied under pressure, which pressures are in some installations quite high. A high pressure fluid brought to an end of the core to flow through the tubes is applied in a manner to attempt a relative approaching motion of the headers. This effort is resisted by the tubes which are attached at their opposite ends to respective headers, as by brazing, mechanical expansion of the like. The applied pressure may be great enough to exceed the columnar strength of the tubes or the integrity of the tube to header joints. Similarly, fluid under pressure introduced between the headers for flow over and around the tubes exerts a force to urge a relative separating motion of the headers. Again, this is a pressure potentially destructive of tubes and tube to header joints.
Insofar as is known to those substantively involved in the preparation of this application, the problem of protecting against potentially damaging fluid pressures in tubular heat exchangers of the kind shown in the Pfouts, et al patent has not been dealt with prior to this invention.